Many vehicles utilize a turbocharger system for increasing the pressure of intake air entering a combustion chamber of an engine. A typical turbocharger system includes a turbocharger and a charge air cooler. The turbocharger may include a shaft having a turbine wheel and a compressor wheel operatively coupled thereto. Exhaust gas exiting the engine drives the turbine wheel to cause a rotation thereof which in turn rotates the compressor wheel. The rotation of the compressor wheel compresses a stream of air to be delivered to the combustion chamber of the engine. The compressing of the air increases both a pressure and a temperature of the air. The charge air cooler is used to cool the compressed air to increase a density of the compressed air, which in turn improves the efficiency of the engine by increasing an amount of oxygen entering the combustion chamber per unit of volume of the compressed air.
There exist situations where the turbocharger may not be able to increase the pressure of the intake air entering the engine to the desired degree due to a lack of pressure of the exhaust gases being used to drive the turbine wheel of the turbocharger. Such a situation may occur when the amount of power delivered by the engine is increasing rapidly, such as when the vehicle is rapidly accelerating from a relatively low speed requiring little demand on the engine. As a result, some turbocharger systems may further include a supplemental electric supercharger for meeting the demands of the engine when the pressure of the exhaust gas exiting the engine is not great enough to rotate the turbine wheel at a desired rotational speed.
The electric supercharger includes an electrically driven compressor wheel that can be activated to operate at a desired rotational speed regardless of the pressure of the exhaust gases exiting the engine. As such, turbocharger systems utilizing both the traditional turbocharger and the supplemental electric supercharger are able to maintain a desired pressure of the intake air delivered to the engine by selectively operating the electric supercharger based on the demands of the engine.
A flow path for the stream of air compressed by the electric supercharger and a flow path for the stream of air compressed by the turbocharger must be recombined upstream of the engine. One issue faced by the introduction of the electric supercharger to the turbocharger system relates to an undesired flow of the compressed intake air exiting the turbocharger back into the flow path for the intake air exiting the electric supercharger at an intersection of the flow paths. The intake air exiting the turbocharger is heated to an extent that the backflow of the intake air towards the electric supercharger can potentially impair the electric supercharger in a manner that shortens an effective life span thereof.
One solution to preventing the backflow of the air towards the electric supercharger includes the use of an electrically controlled valve that is operated to selectively close off the flow path from the electric supercharger when the electric supercharger is not in use. However, the use of an electrically controlled valve is cost prohibitive, increases the energy demands of the vehicle, and requires advanced control schemes for the timing of the electric actuation of each corresponding valve.
It would therefore be desirable to produce a passive one-way valve at the intersection of the flow path for the air compressed by the turbocharger and the flow path for the air compressed by the electric supercharger to prevent an incidence of back flow into the flow path having the electric supercharger or the flow path having the compressor wheel of the turbocharger.